Young men of color who have sex with men (YMCSM, ages 13-29) experience the highest rates of new HIV infections in the U.S., with existing prevention interventions failing to reach most of this hard to reach population. Recent developments in HIV prevention, however, hold promise to help reverse the trend of rising HIV rates in YMCSM, as well as the overall burden of HIV. Pre-exposure prophylaxis (PrEP), an oral antiretroviral regimen taken daily by HIV-uninfected individuals to prevent HIV acquisition, has demonstrated efficacy for reducing HIV acquisition risk in multiple high-risk populations. At the same time, increasingly ubiquitous use of social media (e.g. Facebook, Twitter, online dating sites) by young people, including low- income YMCSM, provides an efficient avenue to identify and reach many otherwise hard to reach YMCSM. The overall goal of this mentored career development award proposal is to develop and pilot-test a social media-based peer-led intervention to promote PrEP uptake in YMCSM. We will use mixed methods and a 'diffusion of innovation' framework to: (1) determine factors associated with interest in and adoption of PrEP among YMCSM; (2) develop Empowering with PrEP (E-PrEP), a social media-based peer-led intervention to increase PrEP uptake in YMCSM; and (3) pilot-test the feasibility and preliminary efficacy of E-PrEP for increasing intention to use and adoption of PrEP by YMCSM. With guidance from a multi-disciplinary team of expert mentors, I will conduct in-person qualitative interviews with users and non-adopters of PrEP to identify current facilitators of and barriers to its uptake. Using the 'diffusion of innovation' theoretical framework to interpret our findings, I ill then partner with YMCSM peer leaders to develop a social media-based intervention to facilitate PrEP uptake. The resulting E-PrEP intervention will use online messaging and discussions directed by peer leaders to provide education on PrEP, increase interest in PrEP use, and facilitate access to PrEP. We will then conduct a pilot randomized trial of E-PrEP (versus exposure to online messaging and discussions promoting general health and nutrition) in YMCSM ages 18-29 to assess E-PrEP's feasibility and preliminary efficacy for increasing self-reported intention in and uptake of PrEP among YMCSM. We hypothesize that, compared to a control group exposed to non-overlapping online contents focused on general health topics, participants randomized to E-PrEP will be more likely to express intention to use and to use PrEP. Once we have preliminarily determined an effect size for E-PrEP's efficacy, we will submit an R01 application to test E-PrEP among YMCSM in a multi-center randomized trial. During the award period, I will develop expertise in social media- and technology-based health interventions, including associated ethical challenges, and I will also pursue advanced training in longitudinal and qualitative data analysis. Completion of my planned research and career development activities will allow me to become an independent investigator of novel bio-behavioral interventions for improving the health of hard to reach populations.